Abyssal 15
Draconic 24
Dwarvish 6
Elvish 9
Giant 19
Goblin 22
Infernal 18
Orc 15
Sylvan 7
In my homebrew campaigns, I treat Draconic like the Middle Ages treatment of Latin: the language of learning and education - and instruction in the ways of magic, of course.
To prevent other characters from reading the Wizard's spellbook "because I know the letters too!", Draconic is written in cuneiform. (Cuneiform looks like something you could scratch out with claws.)
Dragons think most other races write Draconic in very small print.
I don't understand why we need a special language for the forest creatures but plains-dwellers, mountaineers, &c. don't get one.